/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.inlong.common.msg;

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;

/**
 * A reusable {@link java.io.DataInput} implementation that reads from an in-memory buffer.
 *
 * This saves memory over creating a new DataInputStream and
 * ByteArrayInputStream each time data is read.
 *
 * Typical usage is something like the following:
 *
 * DataInputBuffer buffer = new DataInputBuffer();
 * while (... loop condition ...) {
 *   byte[] data = ... get data ...;
 *   int dataLength = ... get data length ...;
 *   buffer.reset(data, dataLength);
 *   ... read buffer using DataInput methods ...
 * }
 */
public class DataInputBuffer extends DataInputStream {

    private static class Buffer extends ByteArrayInputStream {

        public Buffer() {
            super(new byte[]{
                    //
            });
        }

        public void reset(byte[] input, int start, int length) {
            this.buf = input;
            this.count = start + length;
            this.mark = start;
            this.pos = start;
        }

        public byte[] getData() {
            return buf;
        }

        public int getPosition() {
            return pos;
        }

        public int getLength() {
            return count;
        }
    }

    private Buffer buffer;

    /**
     * Constructs a new empty buffer.
     */
    public DataInputBuffer() {
        this(new Buffer());
    }

    private DataInputBuffer(Buffer buffer) {
        super(buffer);
        this.buffer = buffer;
    }

    /**
     * Resets the data that the buffer reads.
     */
    public void reset(byte[] input, int length) {
        buffer.reset(input, 0, length);
    }

    /**
     * Resets the data that the buffer reads.
     */
    public void reset(byte[] input, int start, int length) {
        buffer.reset(input, start, length);
    }

    public byte[] getData() {
        return buffer.getData();
    }

    /**
     * Returns the current position in the input.
     */
    public int getPosition() {
        return buffer.getPosition();
    }

    /**
     * Returns the length of the input.
     */
    public int getLength() {
        return buffer.getLength();
    }

}
